extension

/ɪkˈstɛnʃən/

//ɪkˈstɛnʃən// noun

By · According to Wiktionary data (CC BY-SA) ·

"extension" is a 9-letter English headword indexed on PlainSpell.

The verdict

“extension” has 14 generated spelling variants in the English index at frequency #3,231. The variants make it a useful spelling check.

#3,231
frequency rank, English
2,246
“E” headwords
14
tracked misspellings
3
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed September 2, 2026) - The act of extending; a stretching out; enlargement in length, breadth, or time; an increase.

Corpus desk

Index EN-extension · extension · English

extension · rank #3,231 · 14 variants · 3 confusables

  • FREQ-COMMON #3,231
  • LEN-LONG 9 letters
  • VOW-4 4 vowels
  • CONFUS-LOW 3 pairs
  • VAR-HIGH 14 variants
  • BOOK-MID 2,246
  • PHOTO-FINISH establish

Nearest frequency peer: establish (-1 rank slots)

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Frequency neighbourhood for “extension”

Lower corpus rank = more everyday usage (inverted bar length for readability)

corpus weight

What this shows Bars show where “extension” sits against the nearest ranked English headwords in the FrequencyWords band, not a reprint of letter-browse containment.

Source FrequencyWords open word-frequency list As of September 2, 2026

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

extension vs extensive
78% similar
extension vs extrusion
78% similar
extension vs expansion
78% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for extension
PropertyValue
Headwordextension
LanguageEnglish
Part of speechNoun
IPA/ɪkˈstɛnʃən/
Letters9
Frequency rank#3,231
Misspellings tracked14
Confusable pairs3
SourceWiktionary (kaikki.org)

Where “extension” sits in English frequency

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right). extension lands here:

#1#100#1K#10K#100K
← used constantlyrarely used →

Scale is logarithmic (each tick is 10× rarer). Source: FrequencyWords open word-frequency list.

A misspelling magnet

The generator records 14 spelling variants around extension (IPA /ɪkˈstɛnʃən/), anoun. Corpus frequency is #3,231 among 2,246 “E” headwords. Wiktionary lists 21 senses, so context still picks the gloss.

Our generated misspelling index lists 14 likely wrong-spelling variants for extension, with forms such as "etxension", "exetnsion", and "extenison". Each of these forms differs from the correct spelling by one small edit: a doubled letter, a dropped silent letter, or a substituted vowel. It also participates in 3 confusable-pair relationships, "extensive", "extrusion", "expansion", a pairing that trips writers up because the two words share enough sound or shape to blur together.

Etymologically, the entry records: From Middle English extensioun, from Old French estension, from Latin extensiō, extensiōnem. The correct English form is extension, spelled E-X-T-E-N-S-I-O-N.

Definition

  1. 1
    The act of extending; a stretching out; enlargement in length, breadth, or time; an increase.
  2. 2
    The state of being extended.
  3. 3
    That property of a body by which it occupies a portion of space (or time, e.g. "spatiotemporal extension").
  4. 4
    A short exact sequence 1→H→E→G→1, or the group E therein.
  5. 5
    A short exact sequence 0→B→E→A→0, or the object E therein.
  6. 6
    A part of a building that has been added onto the original.
  7. 7
    An outgrowth; a part of something that extends its capabilities.
  8. 8
    Capacity of a concept or general term to include a greater or smaller number of objects; — correlative of intension.
  9. 9
    semantic widening, broadening of meaning
  10. 10
    A written engagement on the part of a creditor, allowing a debtor further time to pay a debt.
  11. 11
    The operation of stretching a broken bone so as to bring the fragments into the same straight line.
  12. 12
    An exercise in which an arm or leg is straightened against resistance.
  13. 13
    A simple offensive action, consisting of extending the weapon arm forward.
  14. 14
    A numerical code used to indicate a specific telephone in a telecommunication network.
  15. 15
    Ellipsis of file extension.
  16. 16
    An optional software component that adds functionality to an application.
  17. 17
    The set of tuples of values that, used as arguments, satisfy the predicate.
  18. 18
    A kind of derivative morpheme applied to verbs in Bantu languages.
  19. 19
    The ideal in the codomain generated by the image of the given ideal under the given homomorphism.
  20. 20
    University programs that are targeted at the broader (usually adults) community whose participants are not full-time enrolled students.
  21. 21
    Clipping of hair extension, nail extension, or eyelash extension.

Recorded use

Wiktionary examples

These source excerpts show how extension appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. Next month the house is undergoing an extension.
  2. Due to the unforeseen circumstances, you are allowed an extension of two weeks to complete the task.

Etymology

From Middle English extensioun, from Old French estension, from Latin extensiō, extensiōnem.

Synonyms

denotation

Antonyms

shorteninglimitationcurl

This word in other languages

extensión(Español)extension(Français)Ausdehnung(Deutsch)extensão(Português)

Common misspellings

Also misspelled as:

  • etxension
  • exetnsion
  • extenison
  • extennsion
  • extensino
  • extensionn
  • extensoin
  • extenssion
  • extention
  • extesnion
  • extnesion
  • exttension
  • exxtension
  • xetension

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of extension - expressed in single-character edits (insert, delete, or swap one letter). Bigger bars stand out at a glance; a one-edit slip is the hardest to catch.

etxension2exetnsion2extenison2extennsion1extensino2extensionn1extensoin2extenssion1
Edit distance from "extension"

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

PlainSpell is rendered directly from structured Wiktionary extracts and open word-frequency lists, no number is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of September 2, 2026. Primary sources: Wiktionary (via kaikki.org) and FrequencyWords.

Frequently Asked Questions

How do you spell "extension"?
"extension" is spelled E-X-T-E-N-S-I-O-N. The IPA pronunciation is /ɪkˈstɛnʃən/.
What does "extension" mean?
As a noun, "extension" means: The act of extending; a stretching out; enlargement in length, breadth, or time; an increase.
What words are commonly confused with "extension"?
"extension" is commonly confused with "extensive", "extrusion", "expansion". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "extension"?
The IPA (International Phonetic Alphabet) transcription for "extension" is /ɪkˈstɛnʃən/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "extension"?
From Middle English extensioun, from Old French estension, from Latin extensiō, extensiōnem. See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Similar English words by spelling shape

Same letter count and similar misspelling depth for "extension", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 9 letters (nearest by frequency rank).

establish#3,230elsewhere#3,229increases#3,239locations#3,242

Similar misspelling depth

Headwords with a similar count of attested misspellings (14 here; floor ≥5).

processing14 variantsridiculous14 variantsstrongly14 variantssituations14 variants

What to do next

You've looked up "extension". Here's where to go from here.

  • "extension" maps to 3 confusable pairs in this vintage; the highest-scored is "extensive". View pair
  • 14 edit-distance misspelling variants are generated for spell-check research on this headword. See variants
  • Usage frequency rank #3,231 among English headwords in this corpus. Corpus statistics
  • Browse more English words in the "E" letter cohort. E–Z browse

PlainSpell is a reference corpus, not spelling advice. Verify unusual forms in context.

Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list